The present invention relates to an offset printing press for printing securities, which prints on securities such as bank notes.
Japanese Patent Laid-Open No. 2010-221410 discloses an offset printing press for printing securities of this type. This printing press includes a sheet feed device, printing device, sheet delivery device, and inspection device. The sheet feed device feeds paper sheets one by one. The printing device prints on the paper sheets fed from the sheet feed device. The sheet delivery device uses delivery chains to transport and deliver the paper sheets printed by the printing device to a delivery pile. The inspection device inspects print images printed on the paper sheets before they are delivered to the delivery pile. Paper sheets printed by a printing press of this type are processed by anticounterfeit techniques such as embedding of a “watermark”.
In the above-mentioned printing press, to inspect the qualities of paper sheets themselves, the operator carries all paper sheets printed and delivered to the delivery pile from the printing press to a room for inspection, and inspects them by visual inspection or using an inspection device in the inspection room. Therefore, the quality determination criterion in inspection is not stable, a special operator dedicated to inspection is necessary, the operator's burden is heavy, and the productivity lowers. Also, in this inspection method, the qualities of paper sheets are inspected while print images are superimposed on materials embedded in the paper sheets by anticounterfeit techniques. Thus, the print images become a factor which hinders inspection of the qualities of the paper sheets, so the inspection accuracy may degrade.